1. Field of the Invention
The present invention relates to a control/monitor signal transmission system, and more particularly, to a control/monitor signal transmission system with a simple configuration in which a mediation station is installed in place of a PLC (programmable logic controller) and a computer which are control units and a master station. The present invention relates to a concept of a so-called wiring-saving system in which wirings between devices can be omitted in such a way that due to such a configuration, a parallel control signal from a control unit is converted into a serial signal and transmitted, and an actuating device side which is distantly-positioned converts the serial signal into a parallel signal to perform device control. In a regular control in which output with respect to input is constant while performing such wiring omission, as more simple control is performed, a design is simplified, and equipment is simplified. The present invention relates a control/monitor signal transmission system in which, in a regular control in which output with respect to input is constant, a power signal is superimposed onto a transmission signal, and a monitor signal and a control signal are superimposed onto a clock signal.
2. Description of the Related Art
Typically, even control for performing simple input/output control has been performed through determination of a central control system. As a central control system, there are a host computer, a PLC (programmable logic controller), and a wiring-saving master station. Control/monitor signal transmission systems in which the central control systems, and a lamp and an electromagnetic valve which are controlled apparatuses or a wiring-saving output unit (which is a control unit which converts a communication control signal from a parallel signal into a serial signal and combining the serial signal to thereby reduce the number of wirings, and can select and use appropriate units of, for example, at least 1 terminal to 32 terminals) perform communication control, and transmit monitor signals from a plurality of sensor sections (on-off states of, for example, switches and phototransistors) which are distantly-positioned are being widely used in an automatic control technology field.
Meanwhile, in the automatic control technology field, methods for more simply performing communication control have been suggested. For example, Patent Document 1 discloses a control/monitor signal transmission system which includes a plurality of slave stations which are installed corresponding to a plurality of controlled apparatuses and are connected to a common data signal line and corresponding controlled apparatuses, and a mediation station which is connected to a common data signal line and transmits a monitor signal transmitted from a predetermined controlled apparatuses as a control signal of a predetermined corresponding controlled apparatus. In the control/monitor signal transmission system, a mediation station transmits a signal of an input unit to an output unit without involving a control unit in place of a master station, so that simple communication control can be performed without a control section.